The present invention relates to a fluid control device for use in an oil and/or gas well and, more particularly, to such a device for selectively controlling the flow of production fluid from a producing formation adjacent the well, through the well, and to the ground surface.
In a typical oil and gas production well, a casing is provided to line the well and is provided with perforations adjacent the formation to receive the production fluid. A tubing string is run into the casing and has an outer diameter less than that of the inner wall of the casing to form an annulus. A packer is placed in the annulus to direct the production fluid into the lower end of the tubing string for passage upwardly through the tubing string for recovery above ground.
It is often advantageous, and sometimes necessary, to utilize hydraulically-actuated packers and other ancillary devices, especially when operating in deviated or horizontal well sections. To this end, the flow of production fluid into and through the tubing string is blocked, and well fluid is introduced into the tubing string from the ground surface, to create a relatively high fluid pressure which is used to actuate these devices. After this operation is completed the tubing string must be opened to permit the flow pf production fluid through the string and to the ground surface. Therefore, pump-out plugs, or the like, are often provided in the tubing string which normally block fluid flow through the string and which are ejected from the string when the flow of production fluid is desired. However, these plugs are relatively large and, when ejected, must either be removed from the wellbore by coiled tubing or the like, which is very expensive, or left in the wellbore, which may cause problems during the life of the well.
Also, disc subs have been used which incorporate a disc that normally blocks fluid flow through the tubing string and which breaks in response to fluid pressure acting thereon when flow is desired. However, these disc subs suffer from the fact that the pressure that has to be applied to break the disc is often excessive and unpredictable. Therefore, other techniques have been devised to break the discs to permit fluid flow. For example, steel bars have been used which are dropped into the well or run on wireline or coiled tubing. This has disadvantages since the broken disc forms debris in the wellbore and, if the well has a deviated or horizontal section, a drop bar or wireline run is very unreliable.
Still other techniques for selectively blocking the flow of production fluid through the tubing string involve wireline set/retrieved tubing plugs. However, these devices require a "profile" sub that has to be added to the tubing string and require the use of wireline intervention, as well as increased risk and expense.
Therefore, what is needed is a relatively inexpensive and reliable device for selectively controlling the flow of production fluid through a tubing string in an oil and/or gas well which minimizes the amount of debris left in the wellbore yet which can be activated with a predictable and relatively low amount of fluid pressure. Also what is needed is a device of the above type which does not require a profile sub or any actuation device to be dropped into the tubing string or run into the string on wireline or coiled tubing.